This invention relates to an improved process for the recovery of dicalcium phosphate from phosphate rock or ore.
Various wet processes for producing phosphoric acid by acid treating phosphate rock have been described in the literature, such as in Phosphoric Acid edited by A. B. Slack (Marcel Dekker, Inc., New York, 1968). Those processes have focused upon the production of phosphoric acid and have been concerned with the treatment of high grade phosphate rock; and relatively little experience appears to be reported on either the handling of low grade phosphate rock or the production of precipitated dicalcium phosphates. U.S. Pat. Nos. 3,919,395 and 4,012,491 have provided processes for the manufacture of dicalcium phosphate using dilute mineral acids to digest a wide range of phosphate rock. These processes, however, require the use of large quantities of fresh water. Fresh water requirements are also necessitated, as far as it is known, in virtually all wet processes by acid treatment of phosphate rock.